Immediate hypersensitivity (allergy) has been shown to be mediated by a distinct class of immunoglobulins, namely IgE. This antibody binds via its Fc-domains to specific high affinity receptors on the surface of mast cells and basophils. Upon binding of the receptor bound IgE to the polyvalent antigen (the allergen), the IgE-receptors are cross-linked, providing a signal by which the cell is triggered to release histamine and serotonin from their granules into the extracellular space. These compounds are responsible for the pathologic manifestations of allergy (Ishizaka et al., Proc. Natl. Acad. Sci. (U.S.A.), 76:5858 (1979), c.f. Ishizaka, T. et al, Prog. Allerg., 34: 188 (1984)).
The nature and sequence of biochemical processes which couple the IgE-mediated stimulus to mediator secretion from mast cells are topics of considerable research interest and activity. One of the different early events which has been most intensively examined and discussed, is the transient increase in the concentration of free Ca.sup.2+ -ions in the cytosol ([Ca.sup.2+ ].sub.i) of mast cells of different origins. The requirement of millimolar concentrations of Ca.sup.2+ in the extracellular medium for the immunologically triggered secretion has been widely documented and was interpreted to reflect a net influx of these ions into cells, via ion channels, flowing down their concentration gradient. In recent years the discovery of the capacity of inositol triphosphate to release sequestered Ca.sup.2+ -ions from intracellular depots led several investigators to propose, that the source of the transient rise in [Ca.sup.2+ ].sub.i is intrinsic rather than due to a channel mediated influx. IgE-mediated secretion and examination of these ions' influx with .sup.45 Ca.sup.2+ as tracer further supported the notion of a channel opening being the main force of the rise in [Ca.sup.2+ ].sub.i.
Cromolyn has been introduced as a therapeutic drug for allergic asthma under the names Ital and Lomudal (Cox et al., Adv. in Drug Res., 5:115-195 (1970)). Cromolyn is the disodium salt of 1,3-bis-(2-carboxychromone-5'-yloxy)-2-hydroxypropane and is also known as disodium cromoglycate and DSCG. Throughout the present specification and claims, this drug will be referred to as "cromolyn." Whereas many antiallergic drugs exert their effect distal to the histamine release, cromolyn is believed to interface with the mechanism leading to a transiently elevated [Ca.sup.2+ ].sub.i upon antigenic stimulation of the cell. Hence, it prevents the secretion from taking place. In mast cells cromolyn has been shown to inhibit the degranulation and the antigen-induced .sup.45 Ca.sup.2+ -influx to a certain degree (Cox, Nature, 216:1328 (1967); Mazurek, et al., Nature, 303:528 (1983)). This led to the idea that the drug may interact with a certain membranal component, which is involved in the receptor-mediated calcium influx into mast cells and basophils, and has raised the possibility of isolating this component by affinity procedures based on this interaction.
Parent applications Ser. No. 843,912 and 517,843 describe the isolation of such a membrane component from mast cells and basophils. See also Mazurek et al, Proc. Natl. Acad. Sci. U.S.A., 80:6014 (1984); Mazurek et al, EMBO Journal, 1:585-590 (1982); Pecht et al, In: Mast Cell Differentiation and Heterogeneity, Ed. Befus et al, Raven Press, New York, N.Y. (1986). This component was isolated using matrices assumed to be carrying cromolyn. The procedure employed in said earlier application for conjugating commercially available cromolyn to carriers involved a putative alkylation of cromolyn with the bifunctional reagent 2-aminoethane-1-sulfate to yield an amino-derivative that could be cross-linked to amine residues of proteins by glutaraldehyde. Since the date of said earlier application, it has been established that this procedure does not yield the desired conjugation. Although the matrices prepared by this procedure do yield a component, which when assayed in reconstituted lipid planar bilayers exhibits IgE-Fc.sub.e -receptor gated ion channel activity, the amount of active component obtained by this process was so minute that the initial characterization thereof was not entirely accurate. This problem can be traced back predominantly to the failure in covalently conjugating the drug to its carriers.